At the beginning of the level where you reach the security guard, find a chair. It is easily moved. Move it to the door that he will open for you, and get him to open it. Slide the chair in between the doors, and it will not close. This may take a few tries. Go out, take the crowbar, charge it up until you reach the same security guard, and hit him until he explodes. Then, get his pistol with the laser sight and continue the game.

Spawn Grunts:

Enable cheat mode, then use the impulse 76 code to activate the GruntOMatic. A message to start a new game in order for it to work will appear. If you want to continue where you currently are, just quicksave, then quickload the game. Once you have quickloaded, type in the code again to spawn a Grunt. Note: You must have the nocliping code on before you spawn the grunt because he will be spawned close to you. If this is not done, a message stating that the monster spawned is stuck in a wall may appear and the game will end. Do not spawn the Grunt in a closed position or the same message will appear. The Grunt you spawn will see you as a hostile. To have more fun, use the /notarget code and spawn a number of grunts to do your alien hunting. The Grunts you spawn will look like the Grunts from the original HalfLife.

Hidden audio:

Approach the Boss of Opposing Force to hear backwards audio composed of the phrase "To win the game you must kill me Randy Pitchford" when played correctly. Randy Pitchford is the leader of the development team at Gearbox Software.

Original levels:

You can play all the HalfLife levels that Gordon Freeman went through as Adrion Shepard, but in the lab none of the scientists will talk to you.Hints: Save your ammo! If you can take out an enemy with the wrench, use it instead of unloading a clip.

Maintain control of the medic; if you "release" him, other grunts will yell for medical assistance and they'll take the medic's supply of shots, leaving you with nothing.

You can only use the Barnacle on organic materialsthese are usually green, with small lumps. Latch onto them and climb away!

Playing HalfLife differently:

: Mike

Select a custom singleplayer game like "They hunger" or "Opposing Forces".Then use the console and type "map c1a0", now you should play HalfLife as a different person, use all weapons code to get the customs game's weapons.Also, in the case of They Hunger, the characters will look different.

Cheat:

submitted by: German Sargeant

Just like the Spawning grunts,go in the console during the game and type in impulse 76 then exit console and quick save game and quick load it again.Then type it in again. you will have the Grunt in front of you! make sure you have /god mode on,and Notarget on because they will see you as a Hostile.So have some fun watching them attack and die at a huge monster/boss. The Grunts are the ones from HalfLife Original.They won't Follow you. And if you have this cheat. Go in console and type in /map c1a0.Then you go to Sector B where Freeman is. you will have no weapons yet so type in impulse 101 till you get every thing and ammo. Have Fun!

Hint:

By: MustafaEmail:

Shoot the engineer's gas tank from behind him and it will explode!but be sure to be a good distance from him or you will be killed!you can do this several times.Hints:

: jaidev shastri

1 the best way to kill a zombie is to shoot the separating point of the headcrab & the body(the best weapon is a shotgun).

2 the best method to kill any monster is to shoot its head other than the body.

3 the best method to kill your enemy is by using a pipe wrench.the pipe wrench's pressure increases when you hold right mouse button

Hidden programmer message:

At the end of the game while Gman is talking to you in the helicopter, enable the chase_active 1 code to go into third person view. Then, look up through the roof of the helicopter. Printed on the sky will be a hidden programmer message which reads, "Hack hack hack, all day long. Hack hack hack, while a sing this song." (referring to the fact that you will be currently cheating at this moment).

Valve reference:

Enable the brightness 9999999999999 code and go to map of3a4. After the part where you save the scientist in the clean suit and he lets you through the first locked door, there will be a room with three fish tanks. The middle one will be cracked open. Climb up through it and into the dark crawlspace with all the Xen monsters in it. On the walls will be the Valve corporation printing.

Valve, Steam, and Gearbox references:

Go to map of4a4. This is the map with the Pit Worm. Notice that in order to flush the radioactive waste, which kills the worm, you must first complete several tasks. These include opening the Steam vents, the Valves, and activating the Gearbox. These are the names of the major corporations which created the game.See Shepard:

Successfully complete the game and wait until the credits are over. After the screen turns black, enable the brightness 9999999999999 code to see Shepard.

Redo the sniper course:

During boot camp, shoot the trainer and you will start again at the beginning of the course.

Give any gun the magnification of a sniper rifle:

Save with the gun you want to be magnified. Then, switch to the sniper rifle and turn on the scope. While the scope is on, load the previous save.

Vortigaunts on the Hazard Course:

After getting the Displacer on Xen, use the secondary fire before you go through the portal to Earth. You will be warped to the CrouchJump section of the Hazard Course, where one Vortigaunt will attack the holographic instructor. On the other side of the room is a second Vortigaunt and a shotgun. The portal exit is in a corner of the observation room.